Detonation meter calibrator



Feb. 17, 1953 D. R. DE BOISBLANC DETONATION METER CALIBRATOR Filed March l5, 1948 2 SHEETS- SHEET l w n Wmm 'im N INVENTOR.

D. R DE BOISBLANC m N m T T A *www B Feb. 17, 1953 D. R. DE BolsBLANc DETONATION METER CALIBRATOR Filed March 15, 1948 2 SHEETS--SI'IEET 2 INVENTOR.

D.v Y B N m T T A Pntcnted Feb. l?,

DETNATON METER CALIBRATOR Beslonde de Boisblanc, Bartlesville, Okla., as`

signor te llhiliips Petroleum Company, a corporation ci Delaware Application March 15, 1948, Serial No. 14,877

(Cl. Z50-36) 7 Claims. l

This invention relates to a dello-nation meter calibrator for producing an output simulating voltage waves from an electro-mechanical transducer representative ci detonation in the cylinder of an in rnal combustion engine.

In the s of detonations or explosions in internal con bustion engine cylinders, it has befcorne common lractice to utilize an instrument, such as a pic -un, for converting pressure variations in the r into electric currents. The output of such a picnup is fed to a detonation meter w ein the electrical currents are filtered and altered so as to provide a met-er reading indicative or detonation occurring in the cylinder. The or the pick-up output which is of interes ts a relatively slowly varying voltage iv reresentative or the main pressure wave in cylinder and, when the engine is operated under conditions causing knocking or detonation, a peak. or pip is superimposed upon this slowly 1g wave thereby indicating the knocking cor prevalent in the cylinder. The function et the detonation meter is to separate this ton peak from the main pressure wave and from the objecticnal voltage cornponents r from other disturbances, suc

as valve clat With the adoption of such detona-l tion meters, it be" become desirable to provide apparatus for pi. the voltage raves produced by the pick-up device. Ey prod sing such e.. wave and varying the components thereof, a detonaticn meter may be calibrated in terms of the relative detonation intensities caused by test 4fuels of diiering octane number.

It is an object of this invention to provide a calibrating device for producing an output simulating the voltages produced by the pick-ups utilized with detonation meters.

lt is a further object of this invention to provide such a calibrating device in which the configuration and amplitude of the generated waves may be varied to simulate variations in knock ing or detcnation intensity resulting from changes in octane number of the test fuel in a standard engine.

It is a further object of the invention to provide such `a calibration device which is simple in construction, reliable in operation, and economical to build and assemble.

Various other objects, advantages and features of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

icing an output simulating Figure 1 is a block diagram of the detonation meter calibrator;

Figures 2 to 8, inclusive, are graphs illustrating the wave forms in various parts of the calibrator circuit; and

Figure 9 is a schematic circuit diagram showing the complete circuit of the detonaton meter calibrator.

The novel calibration circuit produces an output as indicated in Figure 8, simulating the voltage produced by a detonation pick-up. The wave form consists of a succession of spaced. highly damped waves simulating they respective main pressure waves in a cylinder together with a peak or pip on each damped waves simulating detonations in the cylinder. This output is produced by mixing a sharply decaying pulse with voltage waves produced by av damped resonant circuit, both the differentiating circuit and resonant circuit being excited by spaced pulses from a single multivibrator unit.

Referring now to the drawings in detail, a multivibrator Ill is provided for producing two separate wave forms as indicated, respectively, by Figures 2 and 3. The multivibrator circuit is of generally conventional construction and may include a pair of electron tubes II and I2 each having at least an anode, a cathode, and a control grid. The cathodes of the tubes are both grounded. by a conductor I3 and a pair of resistors I4, I5 are connected between the grids of the respective electron tubes and ground. Current is supplied from a positive terminal Il of the power supply through resistors I8 and I9, ref spectively, to the anodes of the tubes. Further, the anode of tube II and the control grid of tube I2 are interconnected by a condenser 2I while the anode of tube I2 and the control grid of tube II are yinterconnected by a condenser 22. The multivibrator circuit is synchronized by a pulsating Voltage applied to the grid of tube II by a conductor 2li, this conductor including a condenser 25 and extending to the movable arm of a potentiometer 2e which is connected between ground at 21 and a positive terminal 278 of the power supply. lt will be noted that the terminal 28 supplies unltered or pulsating current through potentiometer 25 and condenser 25 to the grid of tube I I thereby controlling operation or the multivibrator at a frequency which is a Sub-multiple cf the alternate current power supply frequency f .As those skilled the art will understand, the Wave form produced at the anode of tube II is controlled by the value of the resistance-capacitance unit I5, 2| and this value is so chosen as to produce an approximately rectangular wave 3| at the anode of tube I| each time the multivibrator circuit is actuated. A small exponential pulse 3Ia of opposite polarity may also be produced at the end of the rectangular Wave but this does not change the operation of subsequent parts of the circuit. Suitable constants for obtaining such a rectangular Wave are a value of 250 mmfd. for condenser 2| and a value of l megohm for resistor I5. In similar fashion, the voltage at the anode of tube l2 is controlled by the values of the resistance-capacitance unit I4, 22 and these values are so chosen as to produce an exponential pulse 33, Figure 3, at the anode of tube I2 each time the multivibrator circuit is actuated. It will be observed that the pulse 33 appears at the anode of tube I2 at practically the same instant that the rectangular wave 3| is terminated. Suitable constants for the resistance-capacitance unit -|4, 22 are a value of .25 mmfd. for condenser 22 and a value of 1 megohm for resistor I 4.

The rectangular wave pulses 3| appearing at the anode of tube II are fed through a coupling condenser 34 and a resistor 35 to the input terminals 36, 31 of a Idamped resonant circuit 49. rI'he input terminal 36 and grounded terminal 3? are interconnected by a potentiometer 4I, the arm of Which is connected to an output terminal 42 of the resonant circuit 40, the other output terminal 43 being grounded at 44, The potentiometer 4I is shunted by a damped resonant circuit consisting of an inductance or choke 46, a condenser 41, and a resistor 48. The values of these components are so chosen that the output of-the circuit 40 is highly damped and only the iirst cycle of the Wave train is of sufficient amplitude as to be of importance in the output of the Calibrating unit. Suitable values for btaining this resul-t are a value of 2.5 henrys for the choke 46, a value of 3 mfd. for condenser 4'! and a value of 1,090 ohms for resistor 48.

Each time a rectangular Wave pulse 3| is produced by the multivibrator circuit, the resonant circuit 4D is shock excited by the sudden change in voltage represented by the Wave front 3Ib, Figure 2. As a result, a highly damped sinusoidal Wave train 49, Figure 4, appears in the circuit 49. It twill be noted that the wave 49 begins `at substantially the same time as the rec tangular wave pulse 3|. The damped resonant circuit 49 is also shock excited lby the sudden change in voltage represented by the end portion 3Ic of the rectangular wave pulse 3|, this change in voltage being in opposite direction from the voltage change represented by the portion 3Ib. This produces a second damped sinusoidal Wave train Figure 5, which is of opposite polarity from the Wave train 49 and Which differs in phase from wave train 49 by the Width of the rectangular Wave pulse 3 I.

The output of the damped resonant circuit 40, which is shown at 52, Figure 6, consists of the algebraic sum of the Wave trains 49 and 5|. Accordingly, -the portion 52a, which is coincident With the rectangular wave pulse 3 I, is of the same shape as the corresponding portion 49a of Wave train 49. The slope of the portion 52a continuously decreases until the curve reaches a peas value 52h at the end of the rectangular wave pulse 3|. Thereupon, the amplitude of the wave train 52 decreases, as is indicated by the portion 52e, the` amplitude of this part of lthe Wave train being the algebraic sum of the waves 49 and 5|.

This decrease in amplitude results from the fact A that .the initial portion 5Ia of Wave 5I is considerably steeper than the corresponding portion 49h of wave train 49. Thus, the slope or" the portion 52e is substantially controlled by thc slope of the portion 5|a. The portion 52e oi curve then merges into a highly damped generally sinusoidal portion 52d.

At the time the rectangular Wave 3| is terminated, the amplitude of the voltage waye 49 at 49o is changing very slowly and it ifs t plitude which determines the height o the voltage peak 52D. A small change in the width of the rectangular Wave will cause the point to shift longitudinally a short distance and this shifting will cause a correspondingly small change in the amplitude at 49e which controls the peak amplitude 52h of the voltage wave As a result, the peak amplitude 525 is substantially independent of small variations in the Width of the rect-angular Wave pulse 3i caused, for example, by power line fluctuations.

The pulses 33 from the multivibrator circuit are fed from the anode of tube I2 to a differentiating circuit BB by a conductor 6I connected to an input terminal 52, the other input terminal 63 being grounded at 64. The differentiatinfjl circuit consists of a condenser 65 connected in series with a resistor 36 and a grounded poterd tiometer 6T, the arm of which is connected to one of a set of output terminals 68, the other out put terminal S8 being grounded. The value of .the condenser `and resistors is so chosen that sharply decaying exponential pulse 69, Figure '17,- of very short duration is produced by the differentiating circuit. Further, due -to the fact that the original pulse 33, which is dierentiatcd by the circuit 60 occurs at the end of the corresponding rectangular wave 3|, each pulse 69 occurs during the first half cycle of the corresponding Wave 52 and while the voltage of Wave is at its peak value. Suitable values for obtaining this result are a value of .001 rnfd. for condenser 95, a. value of 50,000 ohms for resistor 5G, and a value of 1000 ohms for the potentiometer tl'. It Will be apparent that the setting of potentiometer 61 controls the lamplitude of the pulses` 69 produced by the differentiating circuit.

In accordance with the invention, a mixing circuit 10 is provided for superimposing the di*- ierentiated pulses l69 upon the respective voltage `Waves 52. To this end, output terminal 42 is connected by a resistor 1I to an output terminal I2 of the mixer, the other output terminal being grounded at 14. Further, one output terminal 68 is connected by a resistor I5 to output terminal 12 and the termin-als 42, 43 are shunted by a resistor 15. The resulting voltage wave 'il appearing at the output of the mixer is indicated in Figure 8 in which it will be noted that a peak or pip 11a is superimposed upon a component 11b from the output of the damped rescnant circuit 40. The wave vform 'H simulates the voltage waves produced by a detonation pick-up utilized with internal combustion engines. More specically, the portion 11b corresponds to the main pressure Wave caused by reciprocating lmovement of the piston while the peak 'lla cor responds to the disturbance of relatively great amplitude which is produced when a detonation or explosion occurs in the cylinder.

From the terminals '12, 13 the voltage wave shown by Figure 6 is fed through a conventional power amplier and thence to the output terminals of the apparatus. The amplifier 80 is of conventional construction and may include two triodcs di, 52 each having. an anode, a cath'- ofi, and a control grid. The grid of triode 8l connected to the terminal 'l2 while the cath# ode is grounded through a bias resistor S53. The anode oi tube 6i is connected through a resistor to a positive power supply terminal it and Lhrough a coupling condenser tt to the control grid of tube S52. The gain of the amplifier may be varied by a switch t? which is connected in with a resistor Sil, this unit being cond between the anode of tube iii and ground. load resistor t9 is connected between ontrol grid of tube 32 and ground while the anode of this tube is connected directly to a fitive terininal @il of the power supply. The ode circuit of tube 82 includes the primary winding ci a transformer 9i, the ainplied output being taken from the secondary Winding of this transformer. The unit also includes a power supply unit :'32 having a grounded negative termin SI5 and a positive terminal @d from which ntered current is supplied to terminals il, 85

From the 'foregoing description, it Will be apparent that l have provided a Calibrating circuit producing an output simulating voltage Waves representative of detonation in the cylinder of an internal combustion engine. The output, which has the Wave forni il, Figure 8, may be readily controlled by suitable circuit adjusti; nts. '.lhus, the amplitude of the peak or pulse may be varied by adjustment of potentio ieter while the amplitude of the component be varied by adjustment oi the pocotiorneter di. By actuation of svvitch t?, the lei l ci output may be changed by an amount c esponding to the difference in signal height observed on a detonation pick-up when two fuels differing by one octane number are compared. accordingly, by the use of the disclosed circuit, a detonation meter may be readily calibrated in oi the octane number oi test fuels to be ed in a standard engine. described i tor circuit is also advantageous in that peat: value 53h of the voltar wave proced by the circuit il is substantially constant is practically independent of changes in the .oth of the rectangular wave Si caused by power .ine fluctuations in tne niultivi rator circuit.

The disclosed circuit is very advantageous in that both the components and pulses @Si are .crateri by' a single multivibrator circuit. This etiects a considerable saving in the number of parte require-:l and insures that the two components of the output signal have the desired phase relationship since the pulse 35i is produced by the multivibrator at the end of each rec tangular wave 3i. It is a further feature oi the invention that the synchronizing impulses supplie-:l to the multivibrator circuit are derived from the conventional power supply unit by providing terminal 28 from which unfiltered or puleatingr direct current may be drawn and applied to the grid of the multivibrator.

it is important that the resonant circuit 4Q be adequately damped in. order to provide only single eective sinusoidal cycle. This results from the fact that the single damped Wave form shown approximates the shape of the pressure wave observed in the output of a detonation pick-up. if the Wave l were not damped, suc cessive voltage Waves would overlap and thereby produce a Wave forni unlike that shown at 'ii in Figure 6.

While the invention has been described in stant of the other unit being selected .,o

produce a pulse at the end of each rectangu ar Wave, a damped resonant circuit tuned to a 1eduency such that one quarter cycle of the ternating voltage wave produced thereby is ci onant circuit to provide a succession of volt Waves, means for differentiating said expone pulses, and a mixing circuit for superir the dierentiated pulses directly upon tive voltage Waves. i

2. A detonation rnc er calibration device coinprising, in combination, a multivibrator circuit including a pair of resistance-capacitance units, the time constant of'one unit being adjusted to produce a rectangular Wave and the time constant of the other unit being selected so to produce a pulse at the end of each rectangu a damped resonant circuit, means for `ien ng the rectangular Waves to said reso; nt circuit to pro vide a succession of voltage Waves, each wave beine produced by two damned sinusoidal comF ponente of opposite pol v v and different phase, phase diference beine equal to the Wdth ci said .rectangular wave, means for .derentiatins Said exponential pulses, a mixing circuit for superimposing the dierentiated pulses upon the respective voltage Waves, a power ainpl'iler, means for feeding the output of said mixing circuit directly to said power amplifier, and 4for varying the gain of said power 3. ln a detonation meter calibrator, a rn vibrator unit including a pair oi electron each having an anode, a cathode, and a contro grid, a pair of resistance-capacitance units each coupling the control grid of one tube to the anode of the other tube, the time constant ci" one i. sistance-capacitance unit being adjusted so as to produce a succession of rectangular wave-s and the time constant oi the other capacitance unit being adjusted so as to produce an exponential pulse at the end of each tangular Wave, a damped resonant circuit includ'- ing an inductance-capacitance unit and a resistor for discharging said capacitance, said circuit being tuned to a frequency such that one quarter cycle of the alternating voltage wave produced thereby is of equal duration to said rectangular Wave, means for feeding sai-:l rec tangular Waves to said damped resonant circuit thereby to produce a succession of damped voltage waves each consisting essentially of a single cycle, and means for feeding the pulses ro duced by said multivibrator without appreciable time delay to the output of said damped resonant circuit thereby to superimpose the pulses on the first peak portion of the respective voltage waves.

4. In a detonation meter calibrator, a multivibrator unit including a pair of electron tubes each having an anode, a cathode, and a control grid, a pair of resistance-capacitance units each coupling the control grid of one tube to the anode of the other tube, the time constant of one resistance-capacitance unit being adjusted so as to produce a succession of rectangular waves, and the time constant of the other resistance-capacitance unit being adjusted so as to produce an exponential pulse at the end of each rectangular wave, means for feeding a pulsating current to the control grid of one of said tubes thereby to control operation of the multivibrator circuit at a frequency which is a submultiple of the pulsating current frequency, a damped resonant circuit including an inductance-capacitance unit and a resistor for discharging said capacitance, said circuit being tuned to a frequency such that one quarter cycle of the alternating voltage wave produced thereby is of equal duration to said rectangular wave, means for feeding said rectangular Waves to said damped resonant circuit thereby to produce a succession of damped voltage waves each consisting essentially of a single cycle, and means for feeding the pulses produced by said multivibrator without appreciable time delay to the output of said damped resonant circuit thereby to superimpose the pulses on the respective first peak portion of the damped voltage waves.

5. A detonation meter calibration device comprising, in combination, a multivibrator circuit including a pair of resistance-capacitance units, the time constant of one unit being adjusted to produce a rectangular wave and the time constant of the other unit being selected so as to produce an exponential pulse at the end of each rectangular wave, a damped resonant circuit tuned to a frequency such that one quarter cycle of the alternating voltage wave produced thereby is of equal duration to said rectangular wave, means for feeding the rectangular waves to said resonant circuit whereby said circuit is shock excited at the beginning and end of each rectangular Wave, the resulting output of said circuit having a peak value which is substantially independent of the width of the rectangular wave, means for differentiating said exponential pulses, and a mixing circuit for superimposing the diierentiated pulses upon the respective peak portions of the output of the damped resonant circuit thereby to produce a wave from simulating the output of a detonation pick-up.

6. A detonation meter calibration device comprising, in combination, a multivibrator circuit including a pair of resistance-capacitance units, the time constant of one unit being adjusted to produce a rectangular wave and the time constant of the other unit being selectedso as to produce an exponential pulse at the end of each rectangular wave, a damped resonant circuit, means for feeding the rectangular waves to said resonant circuit whereby it is shock excited at the beginning of each rectangular wave to produce a damped sinusoidal wave train, said circuit being shock excited at the end of each rectangular wave to produce a damped sinusoidal wave train of opposite polarity from said rst wave train and displaced in phase therefrom by the width of the rectangular wave, the resulting output of the resonant circuit having a peak value which is substantially independent of the width of the rectangular wave, and means for mixing exponential pulses derived from said multivibrator circuit with the output of said resonant circuit without appreciable time delay to produce a voltage wave simulating the output of a detonation pick-up.

7. A detonation meter calibration device comprising, in combination, a multivibrator circuit including a pair of resistance-capacitance units, the time constant of one unit being adjusted to produce a rectangular wave and the time constant of the other unit being selected so as to produce a pulse at the end of each rectangular wave, a damped resonant circuit tuned to a frequency such that one quarter cycle of the alternating voltage wave produced thereby is of equal duration to said rectangular wave, means for feeding the rectangular waves to said resonant circuit to provide a succession of voltage waves, and a mixing circuit for superimposing said pulses without appreciable time delay upon the respective peak portions of said Voltage waves.

DESLONDE R. DE BOISBLANC.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,426,225 Krause Aug. 26, 193'.' 2,236,705 Campbell Apr. 1, 1941 2,408,079 Labin et al Sept. 24, 1946 2,411,547 Labin et al Nov. 26, 1946 2,416,306 Grieg Feb. 25, 1947 2,434,920 Grieg Jan. 27, 1943 2,434,922 Grieg Jan. 27, 1948 2,438,904 De Rosa Apr. 6, 1948 2,484,352 Miller et al. Oct. 11, 1949 

